U.S. District Magistrate Candy Dale issued the ruling in the case of four same-sex couples who challenged the constitutionality of Idaho's marriage laws, which voters approved as an amendment to the state constitution in 2006.

In her decision, Dale wrote that Idaho's laws barring same-sex marriage unconstitutionally deny gay and lesbian citizens their fundamental right to marry.

"Plaintiffs suffer these injuries not because they are unqualified to marry, start a family, or grow old together, but because of who they are and whom they love," she said.

Dale says the state must issue marriage licenses to same-sex couples starting at 9 a.m. Friday.

Gov. Butch Otter said he will appeal the injunction.

"Today's decision, while disappointing, is a small setback in a long-term battle that will end at the U.S. Supreme Court," Otter said in a statement. "I am firmly committed to upholding the will of the people and defending our Constitution."

Four Idaho couples filed the lawsuit challenging the marriage ban in November, against the governor and Ada County Clerk Chris Rich. The couples are Sue Latta and Traci Ehlers; Lori and Sharene Watsen; Shelia Robertson and Andrea Altmayer; and Amber Beierle and Rachael Robertson.

Latta and Ehlers married in 2008 in California, and the Watsens married in 2011 in New York. Both couples have children and say Idaho wrongly treats Ehlers as a legal stranger to her grandchildren and requires Lori Watsen to obtain a new power of attorney every six months so she can have legal authority to consent to medical treatment for her son.

Their attorney, Deborah Ferguson, said the ruling recognized that the families are part of Idaho's community and that they deserved the same protections and respect as other Idaho families.

"The court's ruling is a victory not only for the courageous couples who brought this case, but for everyone who cares about freedom and fairness," Ferguson said in a statement.

The U.S. Supreme Court ruled last year that a law forbidding the federal government from recognizing same-sex marriages was unconstitutional. Since then, federal judges have ruled against marriage bans in Michigan, Oklahoma, Utah, Virginia and Texas, and ordered Kentucky, Ohio and Tennessee to recognize same-sex marriages from other states.

On Tuesday, a three-judge panel heard an appeal of a federal judge's decision to overturn Virginia's constitutional ban on gay marriage.